JP3972422B2 - Engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an engine control device.
[0002]
[Prior art]
  International Publication No. WO 93/07363 discloses NOx that stores NOx in exhaust when the air-fuel ratio is lean when λ> 1 and releases the NOx when λ ≦ 1 when the air-fuel ratio is lean. An engine control device is described in which an occlusion material is provided and the air-fuel ratio is controlled to be λ = 1 during acceleration operation and full-load operation of the engine and λ> 1 during other operation states. ing. The NOx occlusion material is a NOx occlusion-type catalyst having a function of reducing and purifying NOx. The NOx occluded when the air-fuel ratio is lean is released when the air-fuel ratio becomes rich and is reduced and purified.
[0003]
[Problems to be solved by the invention]
  A basic requirement in engine control is to reduce the fuel consumption rate. For this purpose, it is preferable to make the air-fuel ratio lean in the entire operating range of the engine. Therefore, setting the air-fuel ratio to λ = 1 during the acceleration operation and full load operation of the engine as described above is disadvantageous in terms of improving the fuel consumption because the fuel consumption increases accordingly.
[0004]
  However, when the NOx occlusion material is used, if the air-fuel ratio lean operation continues, the NOx occlusion capacity will be exceeded and discharged into the atmosphere. Therefore, it is necessary to appropriately execute the operation with the air-fuel ratio λ ≦ 1.The
[0005]
  In this way, NOx storageMaterialWhen used, it is preferable to switch the air-fuel ratio appropriately between λ> 1 and λ ≦ 1, but in that case, it is necessary to effectively reduce the amount of NOx discharged into the atmosphere while ensuring fuel efficiency. There is. On the other hand, when the air-fuel ratio is switched from λ> 1 to λ ≦ 1, there is a problem that a torque shock is generated because the output of the engine changes suddenly, and this point needs to be improved.
[0006]
[Means for Solving the Problems]
  In the present invention, the air-fuel ratio does not necessarily have to satisfy λ ≦ 1 over the entire region during the acceleration operation of the engine, and the acceleration performance required when λ ≦ 1 in a specific operation state. Can be ensured, and NOxEnsure NOx storage capacity of storage materialsFor this purpose, attention is paid to the point that it is sufficient to temporarily set the air-fuel ratio to λ ≦ 1.
[0007]
  That is, the invention of this application includes an operating state detecting means for detecting the operating state of the engine,
  The target air-fuel ratio is leaner than the stoichiometric air-fuel ratio (that is, λ> 1) according to the operating state of the engine detected by the operating-state detecting means, and the state near the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio ( That is, in an engine control device comprising air-fuel ratio control means for performing air-fuel ratio control by switching to λ ≦ 1),
It is provided in the exhaust passage of the engine and stores NOx in the exhaust when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and reduces the NOx when it is close to the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio. NOx storage material released for
  Acceleration determination means for determining acceleration operation of the engine;
Shift state detecting means for detecting a shift state of the transmission;
  When the above acceleration operation is determinedThe speed change state detected by the speed change state detecting means is at the gear position of the medium speed ratio.Sometimes the target air-fuel ratio is set near the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio., The above shifting condition is not in the middle gear positionAnd a target air-fuel ratio switching means for setting the target air-fuel ratio to a state leaner than the stoichiometric air-fuel ratio.
[0008]
DThe air-fuel ratio temporarily becomes λ ≦ 1 during engine acceleration.NIn the Ox occlusion material, the occluded NOx can be released. The NOx occlusion material can have its own NOx reduction function to reduce NOx released by itself, or a separate NOx reduction catalyst can be provided to reduce the released NOx. It can also be done.
[0009]
SkyThe control of the fuel ratio includes a fuel injection valve that directly injects fuel into the combustion chamber, and an intake air amount control valve that controls the intake air amount based on the operating state. The air-fuel ratio control can be performed by adjusting the amount.
[0010]
Thus, the acceleration operation of the engine is determined, and from λ> 1 to λ ≦ 1When engine output changes due to air-fuel ratio switching,The shift state of the transmission detected by the shift state detecting means isAt low speeds, the gear ratio is large and torque is easily transmitted. Therefore,In the present invention, the speed change state of the transmission detected by the speed change state detecting means is the gear position at the medium speed ratio.To reduce the torque shock by switching the air-fuel ratio whenI did it.
[0011]
【The invention's effect】
  Therefore, according to the present invention, in an engine control apparatus that performs air-fuel ratio control by switching the target air-fuel ratio between λ> 1 and λ ≦ 1 according to the operating state of the engine, the engine acceleration operation is determined. When, The transmission state of the transmission is in the gear position of medium speed ratioSometimes the target air-fuel ratio is set to λ ≦ 1, The above shifting condition is not in the middle gear positionSometimes the target air-fuel ratio is set to λ> 1,By switching the air-fuel ratio from λ> 1 to λ ≦ 1,NOx without deteriorating fuel consumptionThe NOx occlusion capacity of the occlusion material can be recovered, and the air-fuel ratio control for this recovery is accompanied.Relieve torque shockbe able to.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  <Overall configuration>
  This embodiment relates to a control device for an in-cylinder direct injection engine of an automobile. In FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an intake port, 7 is an exhaust port, 8 is an intake valve, and 9 is an exhaust valve. The cylinder head 3 is provided with an ignition plug 10 facing the center of the combustion chamber 5, and fuel is laterally applied to the combustion chamber side wall of the cylinder head 3 toward the lower side of the ignition plug 10 of the combustion chamber 5. A fuel injection valve 11 for injecting is provided. A cavity 12 is formed at the top of the piston 4, and the cavity 12 reflects the fuel injected from the fuel injection valve 11 to the vicinity of the spark plug 10. An exhaust purification catalyst 14 is provided in the exhaust passage 13 extending from the exhaust port 7. An intake passage 15 connected to the intake port 6 is provided with an electronically controlled throttle valve 16 that is mechanically disconnected from the accelerator pedal and drives the throttle valve by a motor based on the accelerator operation amount and the operating state. .
[0013]
  The operation of the fuel injection valve 11 and the throttle valve 16 is controlled by the control means 17. For this purpose, the control means 17 includes the engine speed, the accelerator opening, the intake air amount, the vehicle speed, and the transmission speed. Signals from various sensors for detecting the gear position and the like are given.
[0014]
  <Exhaust gas purification catalyst>
  The configuration of the exhaust purification catalyst 14 is shown in FIG. In this structure, a NOx occlusion material layer 22 and a catalyst material layer 23 are formed in layers on the carrier 21 with the former facing down (inside) and the latter facing up (outside). The carrier 21 is a cordierite honeycomb structure. The NOx occlusion material layer 22 is composed mainly of an NOx occlusion type catalyst material in which a Pt component as a catalyst component and a Ba component as an NOx occlusion material are supported on activated alumina having a large specific surface area. The catalyst material layer 23 is composed mainly of a NOx reduction type catalyst material in which zeolite is supported as a support base material and Pt component and Rh component are supported thereon.
[0015]
  <Air-fuel ratio control>
  The control means 17 uses a computer, such as engine operation zone determination, acceleration determination, specific operation state determination, fuel injection valve 11 injection timing / injection pulse width calculation, throttle valve 16 opening calculation, and the like. To do. These are done with reference to an electronically stored map. The operation zones are shown in FIG. 3, and the operation range of low or medium rotation and low or medium load is the lean operation zone (A / F = 22 or more), and the other is the enrichment zone (A / F). = 12-14). In this embodiment, the pulse width of the fuel injection is expanded so that the air-fuel ratio becomes λ = 1 (near A / F = 14.7) only when the engine is in a specific operation state in the lean operation zone. The throttle opening is corrected for reduction.
[0016]
  (Main routine)
  The main routine of the fuel injection control is shown in FIG. The engine speed, vehicle speed, accelerator opening, gear position of the transmission, measured value of the air flow sensor, etc. are read and lean based on the engine speed and the engine load (the filling efficiency Ce obtained from the measured value of the air flow sensor). It is determined whether or not it is an operation zone (steps S1 and S2). In the lean operation zone, an A / F correction coefficient Caf for calculating the injection pulse width Ta is calculated, and the pulse width Ta is obtained by the following equation (steps S3 and S4).
[0017]
    Ta = KGKF × Caf × Ce
  KGKF is a fuel flow coefficient. Λ = 1 when Caf = 1, and λ> 1 when Caf <1.
[0018]
  Then, when the predetermined injection timing is reached, fuel injection by the fuel injection valve 11 is executed (steps S5 and S6). When the operation region is other than the lean operation zone, the injection pulse width corresponding to the operation state is calculated and the fuel injection is executed in the same manner (steps S2 → S7 → S5).
[0019]
  (Throttle valve control)
  As shown in FIG. 5, it is determined whether or not the vehicle is in the lean operation zone based on the accelerator opening, the engine speed, and the air flow sensor measurement value (steps S11 and S12). If the characteristic is selected and the vehicle is not in the lean operation zone, the throttle opening characteristic of TVA is selected and the throttle valve is driven (steps S13 to S15). The throttle opening characteristics of TVB and TVA are shown in FIG. 6, and the throttle opening characteristics TVA in the operation region other than the lean operation zone shows that the throttle opening is almost fully closed when the accelerator is fully closed. This is a characteristic that the throttle opening gradually increases as the degree increases. The throttle opening characteristic TVB in the lean operation zone has a predetermined throttle opening TVI even when the accelerator is fully closed, and the throttle opening gradually increases as compared with TVA as the accelerator opening increases.
[0020]
  Although the throttle valve is controlled in this embodiment, the accelerator means and the throttle valve are connected by a wire, a bypass passage that bypasses the throttle valve is provided in the intake system, and a control valve is provided in the bypass passage. This may be controlled so as to produce a similar effect following the control of the throttle valve.
[0021]
  (Caf calculation subroutine)
  Here, the air-fuel ratio is switched between λ> 1 and λ = 1 by the correction coefficient Caf, and λ = 1 is set when the engine is in a specific operating state. Below, each case of the specific driving | running state is demonstrated.
[0022]
  -Λ≤1- in the high vehicle speed driving range
  This is a case where λ = 1 when the engine is accelerating and in the high vehicle speed driving range. As shown in FIG. 7, it is determined whether or not the engine is in an acceleration operation state (step A1). In other words, the acceleration operation state is determined when the rate of increase in the engine speed, engine load Ce, or throttle opening is equal to or greater than a predetermined value. When the engine is in an acceleration operation state, it is determined whether or not the vehicle speed is equal to or higher than a predetermined vehicle speed. If the vehicle speed is high, Caf = 1 is set. At this time, Caf is obtained by referring to the electronically stored map based on the engine speed and engine load Ce at that time (steps A2 to A4). This map is for air-fuel ratio lean operation, and Caf <1.
[0023]
  FIG. 8 shows an example of a running pattern of an automobile. The thick line portion in the figure is a high vehicle speed operation region at the time of acceleration, and at this time, the air-fuel ratio becomes λ = 1. FIG. 9 shows changes over time in the accelerator opening, the vehicle speed, and the throttle opening. The throttle opening is changed from λ> 1 to λ = 1 when the vehicle speed in the latter half of acceleration is increased. Will change. That is, it can be seen that the amount of change in the throttle opening is small and the torque shock is small as compared with the case of switching from λ> 1 to λ = 1 in the early stage of acceleration.
[0024]
  This high vehicle speed operation region is when the engine combustion temperature is high and the amount of NOx emissions increases. At this time, λ = 1, so that the NOx purification rate in the catalyst material layer 23 of the exhaust purification catalyst 14 becomes high. NOx in the exhaust gas is efficiently reduced and purified, and NOx previously stored in the NOx storage material layer 22 is released and reduced and purified by the catalyst material layer 23. Therefore, the storage capacity of the NOx storage material layer 22 is restored.
[0025]
  Further, when λ = 1 in the high vehicle speed driving range, it means that the acceleration of the automobile is enhanced, which is advantageous for overtaking other automobiles.
[0026]
  FIG. 10 shows an example in which the high vehicle speed operating range of the engine is determined based on the engine speed. That is, in step A2, it is determined whether or not the engine speed is equal to or higher than a predetermined value. When the engine speed is equal to or higher than the predetermined value, Caf = 1 is set and the air-fuel ratio is controlled to λ = 1. FIG. 11 shows an example in which the high vehicle speed operating range of the engine is determined based on the engine load. That is, in step A2, it is determined whether or not the engine load is equal to or greater than a predetermined value. When the engine load is equal to or greater than the predetermined value, Caf = 1 is set and the air-fuel ratio is controlled to λ = 1. Whether it depends on the engine speed or the engine load, the effect is the same as in the case of the vehicle speed.
[0027]
  FIG. 12 shows a flow in the case where the air-fuel ratio is set to λ = 1 when the vehicle is once shifted from the start acceleration state to the steady running and further enters the acceleration operation state at a predetermined vehicle speed or higher. That is, λ = 1 is set in the operating state indicated by a thick line in FIG.
[0028]
  In FIG. 12, FlagLspeed is a flag that is "1" when the vehicle speed is zero or low, and FlagCaf1 is a flag that is "1" when accelerating while λ = 1. In the drawing, FlagLspeed = 1 and FlagCaf = 0 (Steps B1 to B3) because the vehicle speed is initially equal to or lower than the predetermined vehicle speed. Therefore, even if acceleration is determined in step B4, since FlagLspeed = 1, Caf is read from the map and Caf <1 is set (steps B4 to B6).
[0029]
  Next, when the vehicle speed exceeds the predetermined speed after starting acceleration and shifts to steady running, the step proceeds from B1 → B3 → B4. However, since acceleration is not determined in step B4, FlagLspeed is cleared (step B7). When shifting from this state to acceleration operation, acceleration is determined in step B4, and FlagLspeed = 0 is determined in step B5. Therefore, FlagCaf1 = 1 and Caf = 1 are set (steps B8 and B9). That is, acceleration operation at λ = 1 is performed.
[0030]
  Next, when the acceleration operation is completed, FlagCaf1 = 1, so the step proceeds from B3 to B10, where acceleration is not determined. FlagCaf1 is cleared, Caf is read from the map, and Caf <1. (Step B11 → B6).
[0031]
  Therefore, since the air-fuel ratio becomes λ = 1 only in the driving state in which the vehicle is accelerated from the steady running state at a predetermined vehicle speed or higher, the same effect as in the previous case can be obtained.
[0032]
  -Λ≤1- early in acceleration
  This is a case where λ = 1 in the early stage of acceleration of the engine, and is shown in FIG. In the figure, FlagAcc is a flag which is “1” when in the initial acceleration state. The Acc timer counts the time after entering the acceleration operation state, and means that the acceleration is in the initial stage during the set.
[0033]
  First, it is determined whether or not the engine is in an acceleration operation state (step C1). If FlagAcc is not 1, even in the acceleration operation state, the acceleration operation state has been entered. Therefore, FlagAcc = 1 is set, the Acc timer is set, Caf = 1, and the air-fuel ratio is λ = 1. (Steps C2 to C5). While the Acc timer is set, the step proceeds from C1 to C2 to C6, and since it is determined that the Acc timer is being set in step C6, Caf = 1 remains (step C6 to C5). When the count of the Acc timer is completed, FlagAcc is cleared, Caf is read from the map, and Caf <1 and thus λ> 1 is set (steps C6 to C8). Even when the engine is not in the acceleration operation state, Caf is read from the map (step C1 → C8).
[0034]
  In the driving pattern of the automobile shown in FIG. 15, when the control flow is executed, the air-fuel ratio becomes λ = 1 at the initial stage of acceleration indicated by the bold line in FIG. By setting λ = 1 at the initial stage of acceleration, it becomes easy to ensure necessary acceleration, and the NOx is efficiently purified by the catalyst material layer 23 of the exhaust purification catalyst 14 in spite of a large amount of NOx emission. The Further, NOx occluded in the NOx occlusion material layer 22 during the previous run or the previous run is released and decomposed, so that the NOx occlusion capacity necessary for the run with the current air-fuel ratio lean is ensured. The
[0035]
  FIG. 16 shows a control flow in which the air-fuel ratio is set to λ = 1 at the initial stage when the vehicle starts to accelerate. That is, if the vehicle speed is less than or equal to the predetermined vehicle speed, FlagLspeed = 1 (steps D1 and D2). If it is now in the acceleration operation state and FlagLspeed = 1, it means a start acceleration state. If FlagAcc = 1, this is set to “1”, and the Acc timer is set (steps D3 to D7). This is an initial state of starting acceleration, where Caf = 1 and the air-fuel ratio becomes λ = 1 (step D8).
[0036]
  Then, Caf = 1 (λ = 1) is held as the initial acceleration state as long as each determination in the acceleration operation state, FlagLspeed = 1, FlagAcc = 1, and Acc timer set is satisfied (steps D3 to D5 → D9). → D8). When the count of the Acc timer is completed, FlagAcc and FlagLspeed are cleared, and Caf is read from the map so that λ> 1 (steps D9 → D11 → D12 → D10).
[0037]
  When the vehicle speed is not lower than the predetermined vehicle speed, FlagLspeed does not become “1”. Therefore, Caf is read from the map and Caf <1 even when the vehicle is not accelerating (steps D1 → D3, D4 → D10).
[0038]
  In the traveling pattern of the automobile shown in FIG. 17, when the above control flow is executed, the air-fuel ratio becomes λ = 1 at the beginning of start acceleration indicated by the bold line in FIG. The initial stage of starting acceleration is when the load is high and the amount of NOx emission is large. However, when the air-fuel ratio becomes λ = 1, it becomes easy to ensure the necessary acceleration and the NOx is a catalyst material layer of the exhaust purification catalyst 14. 23 is efficiently purified. In addition, NOx stored in the NOx storage material layer 22 during the previous run is released and decomposed.
[0039]
  FIG. 18 shows a flow in the case where the air-fuel ratio is set to λ = 1 at the initial stage after the transition from the start acceleration state to the steady running and the acceleration operation state at a predetermined vehicle speed or higher. That is, λ = 1 is set in the operating state indicated by the thick line in FIG.
[0040]
  In FIG. 18, when the vehicle is started, if the vehicle speed is less than the predetermined vehicle speed, FlagLspeed = 1, and FlagLspeed = 1 even in the acceleration operation state, so Caf is read from the map. > 1 (steps E1 to E5).
[0041]
  When the vehicle speed becomes equal to or higher than the predetermined vehicle speed and a transition is made to the steady running state, FlagLspeed is cleared (steps E1 → E3 → E6). After that, when shifting to the acceleration operation state, FlagLspeed is cleared, so the step proceeds from E3 → E4 → E7. If FlagAcc = 1, this is set to “1”, the Acc timer is set, and Caf = 1. (Λ = 1) (Steps E7 to E10). That is, as long as the acceleration is in an initial state after steady running and the Acc timer is being set, Caf = 1 (λ = 1) is maintained (step E11 → E10), and when the Acc timer count ends, FlagAcc is cleared. , Caf is read from the map, so that λ> 1 (steps E11 → E12 → E5).
[0042]
  Therefore, the air-fuel ratio is switched from λ> 1 to λ = 1 only when the amount of NOx emission is large and acceleration is required at the beginning of acceleration during traveling at a predetermined vehicle speed or higher. Thus, it is possible to satisfy the acceleration request while suppressing the discharge of NOx into the atmosphere.
[0043]
  -Λ = 1-at the predetermined gear position
  This is a case where the air-fuel ratio is set to λ = 1 only when the transmission is at a predetermined acceleration gear position even when the engine is in the acceleration operation state, and is shown in FIG. When the condition that the engine is in an accelerating operation state and is in a predetermined gear position (for example, a medium speed acceleration stage that is the second speed or the third speed and not the lowest speed or the highest speed), Caf = 1 is set. Thus, the air-fuel ratio becomes λ = 1 (steps F1 to F3), and when any of the conditions is missing, Caf is read from the map, and Caf <1, and thus λ> 1 (step F4).
[0044]
  In the driving pattern of the automobile shown in FIG. 21, when the control flow is executed, the air-fuel ratio becomes λ = 1 in the driving state indicated by the bold line in FIG. In this case, since the air-fuel ratio is switched when the gear ratio is high, torque shock is alleviated.
[0045]
  FIG. 22 shows a flow in the case where the air-fuel ratio is set to λ = 1 when the vehicle is in a predetermined gear position during start acceleration. That is, λ = 1 is set in the operating state indicated by the thick line in FIG.
[0046]
  In FIG. 22, since the vehicle is initially below a predetermined vehicle speed, FlagLspeed = 1 and FlagCaf = 0 (steps G1 to G3). When the acceleration operation state is determined, FlagLspeed = 1, so if it is in the predetermined gear position, FlagCaf1 = 1 and Caf = 1 are set (steps G4 to G8). That is, acceleration operation at λ = 1 is performed. Thereafter, when the acceleration operation is completed, FlagLspeed and FlagCaf are cleared, Caf is read from the map, and λ> 1 is satisfied (steps G3 → G9 to G12). If the gear position changes even during acceleration operation, Caf is read from the map and λ> 1 (steps G9 → G5 → G12).
[0047]
  Therefore, it is possible to mitigate torque shock when the air-fuel ratio is switched from λ> 1 to λ = 1 during start acceleration.
[0048]
  FIG. 24 shows a flow in the case where the air-fuel ratio is set to λ = 1 when the vehicle is in a predetermined gear position when the vehicle is in the acceleration operation state at a predetermined vehicle speed or higher after the transition from the start acceleration state to the steady driving. That is, λ = 1 is set in the operating state indicated by the thick line in FIG. Therefore, the control flow is the same as in FIG. 12, but it is determined whether or not the gear is in a predetermined gear position when FlagLspeed = 1 is not satisfied in step H5, and the step of setting Caf = 1 (λ = 1) when Yes. The process advances to H8 and H9, and the difference is that the process advances to Step H6 to read Caf from the map when No, and Step H12 is entered. Note that FIG. 12 and FIG. 24 correspond to the same step number performing the same processing.
[0049]
  Therefore, in the case of this control, the torque shock when the air-fuel ratio is switched from λ> 1 to λ = 1 when accelerating from steady running can be mitigated. In particular, an engine with a manual transmission is preferable.
[0050]
  -Λ = 1 at the time of transition to steady driving
  This is not to switch the air-fuel ratio when the engine is in the acceleration operation state, but to switch the air-fuel ratio when shifting from the acceleration operation to the steady running operation, as shown in FIG. .
[0051]
  In the figure, an “accend timer” counts the time for which the air-fuel ratio is λ = 1 when the acceleration operation is shifted to the steady operation. First, if it is in the acceleration operation state, FlagAcc indicating that is set to “1” and Caf is read from the map, so that the air-fuel ratio is set to λ> 1 (steps J1 to J3). Thereafter, when the acceleration operation state is shifted to the steady running state, FlagAcc is cleared, the accend timer is set, Caf = 1 is set, and the air-fuel ratio is switched to λ = 1 (steps J1 → J4 to J7). When the Accend timer count ends, Caf is read from the map, and the air-fuel ratio returns to λ> 1 (steps J8 → J3).
[0052]
  In the driving pattern of the automobile shown in FIG. 27, when the control flow is executed, the air-fuel ratio becomes λ = 1 in the driving state indicated by the bold line in FIG. In this case, the air-fuel ratio becomes λ = 1 at the end of the acceleration operation, so that NOx previously stored in the NOx storage material is released and reduced, and the storage capacity is ensured. In addition, since the air-fuel ratio is switched when the driver travels from the accelerated travel to the steady travel, torque shock is not a problem.
[0053]
  FIG. 28 shows a control flow when the air-fuel ratio is switched to λ = at the end of start acceleration. That is, λ = 1 is set in the operating state indicated by the thick line in FIG.
[0054]
  When the vehicle is started, Flaglspeed = 1 is set if the vehicle speed is equal to or lower than the predetermined vehicle speed, and FlagAcc = 1 is set if the vehicle is in an acceleration operation state. (Steps K1 to K5). After that, if the transition is made from the acceleration running to the steady running, since FlagLspeed = 1 and FlagAcc = 1, FlagAcc is cleared, the Accend timer is set, Caf = 1 is set, and the air-fuel ratio becomes λ = 1. Switching (steps K3 → K6 to K10). When the Accend timer count ends, FlagLspeed is cleared and Caf is read from the map, so that the air-fuel ratio becomes λ> 1 (steps K11, K12 → K5).
[0055]
  Accordingly, NOx occluded in the NOx occlusion material until the end of the start acceleration is released and reduced, and the capacity is restored, and torque shock does not become a problem.
[0056]
  FIG. 30 shows a flow when the air-fuel ratio is set to λ = 1 at the time of completion of acceleration when starting acceleration traveling → steady traveling → accelerated traveling. That is, λ = 1 is set in the operating state indicated by the thick line in FIG.
[0057]
  When the vehicle is started, FlagLspeed is set to “1” when the vehicle speed is lower than the predetermined vehicle speed, and FlagAcc is set to “1” when the vehicle is in an acceleration operation state. λ> 1 (steps L1 to L5). Then, FlagLspeed is cleared when the vehicle shifts to steady running (steps L6 and L7). After this FlagLspeed is cleared, it will be in an accelerated running state. After that, when shifting to steady running, FlagLspeed has already been cleared this time, so when FlagAcc = 1, it is cleared and the Accend timer is set. , Caf = 1, and the air-fuel ratio becomes λ = 1 (steps L6 → L8 to L11). When the Accend timer count ends, Caf is read from the map, and the air-fuel ratio returns to λ> 1 (steps L8 → L12 → L5).
[0058]
  Therefore, after a high speed operation (high load operation) that is accelerated while driving and has a large amount of NOx emission is performed, the NOx previously stored in the NOx storage material is released and reduced, and the capacity is restored. Torque torque is not a problem.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of an engine control device.
FIG. 2 is a cross-sectional view of an exhaust purification catalyst.
FIG. 3 is a map diagram showing engine operation zones.
FIG. 4 is a flowchart of a main routine of air-fuel ratio control (fuel injection control).
FIG. 5 is a flowchart of throttle valve control.
FIG. 6 is a graph showing a throttle opening characteristic TVB in a lean operation zone and a throttle opening characteristic TVA in a non-lean operation zone.
FIG. 7 is a flowchart of a Caf calculation subroutine for executing λ = 1 in the high vehicle speed driving range based on the vehicle speed.
FIG. 8 is a time chart showing a λ = 1 section according to the subroutine.
FIG. 9 is a time chart of accelerator opening, vehicle speed, and throttle opening.
FIG. 10 is a flowchart of a Caf calculation subroutine for executing λ = 1 in the high vehicle speed operation region based on the engine speed.
FIG. 11 is a flowchart of a Caf calculation subroutine for executing λ = 1 in the high vehicle speed operation region based on the engine load.
FIG. 12 is a flowchart of a Caf calculation subroutine for executing λ = 1 in a high vehicle speed driving range during acceleration during traveling.
FIG. 13 is a time chart showing a λ = 1 section according to the subroutine.
FIG. 14 is a flowchart of a Caf calculation subroutine for executing λ = 1 in the early stage of acceleration.
FIG. 15 is a time chart showing a λ = 1 section according to the subroutine.
FIG. 16 is a flowchart of a Caf calculation subroutine for executing λ = 1 at the beginning of start acceleration.
FIG. 17 is a time chart showing a λ = 1 section according to the subroutine.
FIG. 18 is a flowchart of a Caf calculation subroutine for executing λ = 1 in the early stage of acceleration during traveling.
FIG. 19 is a time chart showing a λ = 1 section according to the subroutine.
FIG. 20 is a flowchart of a Caf calculation subroutine for executing λ = 1 at a predetermined gear position during acceleration.
FIG. 21 is a time chart showing a λ = 1 section according to the subroutine;
FIG. 22 shows a Caf calculation subroutine for executing λ = 1 at a predetermined gear position during start acceleration.Flow diagram.
FIG. 23 is a time chart showing a λ = 1 section according to the subroutine.
FIG. 24 is a flowchart of a Caf calculation subroutine for executing λ = 1 at a predetermined gear position at the time of acceleration during traveling.
FIG. 25 is a time chart showing a λ = 1 section according to the subroutine;
FIG. 26 is a flowchart of a Caf calculation subroutine for executing λ = 1 at the end of acceleration.
FIG. 27 is a time chart showing a λ = 1 section according to the subroutine;
FIG. 28 is a flowchart of a Caf calculation subroutine for executing λ = 1 at the end of start acceleration.
FIG. 29 is a time chart showing a λ = 1 section according to the subroutine.
FIG. 30 is a flowchart of a Caf calculation subroutine for executing λ = 1 at the end of acceleration from steady running.
FIG. 31 is a time chart showing a λ = 1 section according to the subroutine;
[Explanation of symbols]
    1 Engine body
    5 Combustion chamber
  10 Spark plug
  11 Fuel injection valve
  13 Exhaust passage
  14 Exhaust gas purification catalyst
  15 Intake passage
  16 Throttle valve
  17 Control means
  21 Carrier
  22 NOx storage layer
  23 Catalyst material layer

Claims (1)

An operating state detecting means for detecting the operating state of the engine;
The target air-fuel ratio is switched between a state leaner than the stoichiometric air-fuel ratio and a state near the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio in accordance with the engine operating state detected by the operating state detecting means. In an engine control device comprising air-fuel ratio control means for performing,
It is provided in the exhaust passage of the engine and stores NOx in the exhaust when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and reduces the NOx when it is close to the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio. NOx storage material released for
Acceleration determination means for determining acceleration operation of the engine;
Shift state detecting means for detecting a shift state of the transmission;
When the acceleration operation is determined, the target air-fuel ratio is in the vicinity of the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio when the gear-shift state detected by the gear-shift-state detecting means is at the gear position of the medium gear ratio. And a target air-fuel ratio switching means for setting the target air-fuel ratio to a state leaner than the stoichiometric air-fuel ratio when the speed change state is not at the medium gear ratio. Control device.

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